1. Field of the Invention
The present invention relates to a motor driving controller for drivingly controlling motors attached to a machine tool, industrial equipment, robot, etc.
2. Description of the Related Art
In a motor driving controller that drive axes of a machine tool, industrial equipment, robot, etc., commercial AC power is temporarily converted into DC power, and then the DC power is converted into AC power of optional frequency and used to drive the motors drivingly. More specifically, the conventional motor driving controller is provided with an AC/DC converter circuit for converting commercial AC power into DC and motor driving DC/AC converter circuits for converting the DC power, the output of the AC/DC converter circuit, into AC power of optional frequency.
The motor driving controller comprises one AC/DC converter circuit and motor driving DC/AC converter circuits as many as the control axes (or motors) of the machine tool, industrial equipment, or robot to be controlled. For controlling motors for the peripheral device, that is, peripheral axis motors, another motor driving controller, which includes an AC/DC converter circuit and motor driving DC/AC converter circuits, or an AC/DC conversion device and DC/AC conversion devices are additionally used.
FIG. 3 shows an example in which a motor driving controller is additionally used to drive the peripheral axes. In this example, a motor driving controller 101 for the axes of a robot 120 is provided with motors 111a, 111b and 111c as motors for the peripheral axes. The motor (motor for servo gun) 111a is used to drive the tip of a spot welding gun that is attached to the wrist of a robot arm. The motor 111b is a traveling axis motor that is used to run the robot. The motor 111c is used to drive a positioner for positioning and feeding a workpiece or the like. Motor driving controllers 110a, 110b and 110c for drivingly controlling the motors 111a, 111b and 111c for robot peripheral axes are attached to the controller 101 that drives the motors of the robot 120.
The motor driving controller 101 that drivingly controls the motors for the axes of the robot 120 comprises one AC/DC converter circuit 102 for converting commercial AC power into DC power and DC/AC converter circuits 103-1 to 103-n for motor drive as many as the control axes of the robot 120. The DC/AC converter circuits 103-1 to 103-n convert the DC power, the output of the AC/DC converter circuit 102, into AC power of optional frequency and drive the motors.
The motors for the control axes of the robot 120 are drivingly controlled by means of the motor driving controller 101, whereby the robot 120 is operated. If the peripheral axes of the robot; such as axis of a servo gun, traveling axis, or positioner, are drivingly controlled, the motor driving controllers 110a, 110b and 110c as shown in FIG. 3 are used. Each of the motor controllers 110a, 110b and 110c is provided with an AC/DC converter circuit 112 and a motor driving DC/AC converter circuit 113. The AC/DC converter circuit 112 converts commercial AC power into DC power. The DC/AC converter circuit 113 converts the DC power, the output of the AC/DC converter circuit 112, into AC power of optional frequency.
Servo control circuits, which comprises a speed control circuit, position/speed control circuit, current control circuit, etc. for controlling the DC/AC converter circuits 103-1 to 103-n, in the controller 101 for driving the motors for respective axes of the robot 120, and controlling the respective positions, speeds, and currents of the motors for the axes of the robot 120, may be provided in the controller 101 or a robot controller or a host controller of the controller 101. Alternatively, the servo control circuits may be provided independently of these devices. In controlling the speeds, the speed control circuit and the current control circuit control the DC/AC converter circuits 103-1 to 103-n in response to a command from the robot controller serving as a host computer. In also controlling the positions, the position control circuit, the speed control circuit, and the current control circuit control the DC/AC converter circuits 103-1 to 103-n, thereby controlling the positions, speeds, and torques.
Further provided are servo control circuits, such as a position control circuit, speed control circuit, current control circuit, etc. for driving the respective DC/AC converter circuits 113 of the motor driving controllers 110a, 110b and 110c that are used drivingly to control the motors 111a, 111b and 111c for the peripheral axes of the robot. In many cases, the motors 111a, 111b and 111c for the peripheral axis of the robot are controlled in synchronism with the robot 120. Accordingly, their servo circuits, along with the respective servo control circuits of the DC/AC converter circuits 103-1 to 103-n of the motor driving controller 101, are controlled by means of the robot controller.
In the prior art example shown in FIG. 3, the motor driving controllers 110a, 110b and 110c comprising the AC/DC converter circuits 112 and the motor driving DC/AC converter circuits 113 for the motors 111a, 111b and 111c which drivingly controls peripheral axes of the robot must be additionally provided. Accordingly, such peripheral axes cannot be added at low cost.
FIG. 4 shows another prior art example of addition of the motor driving controller for peripheral axes. The motor driving controllers 110a, 110b and 110c of the prior art example shown in FIG. 3 are replaced with one AC/DC converter circuit 210 and motor driving DC/AC converter circuits 211a, 211b and 211c for motors 212a, 212b and 212c for peripheral axes. The AC/DC converter circuit 210 converts commercial AC power into DC power. On receiving the converted DC power, the DC/AC converter circuits 211a, 211b and 211c convert the DC power into AC power of optional frequency, thereby drivingly controlling the motors 212a, 212b and 212c for peripheral axes. This example shares other particulars with the prior art example shown in FIG. 3.
The AC/DC converter circuit 210 and the motor driving DC/AC converter circuits 211a, 211b and 211c must be also added in this case, so that the addition of the peripheral axis control costs high.
FIG. 5 shows a motor driving controller 301 for controlling motors for the axes of a robot as a prior art example, in which motor driving DC/AC converter circuits for peripheral axes are provided in advance.
Motor driving DC/AC converter circuits 303a, 303b and 303c for drivingly controlling peripheral axis motors 304a, 304b and 304c for a robot 320, besides motor driving DC/AC converter circuits 303-1 to 303-n for drivingly controlling motors for the axes of the robot 320, are provided in the motor driving controller 301. In the example shown in FIG. 5, the three motor driving DC/AC converter circuits are provided in advance. The controller 301 is provided with only one AC/DC converter circuit 302 for converting AC power into DC power. The DC power or the output of the converter circuit 302 is applied to the motor driving DC/AC converter circuits 303-1 to 303-n and the DC/AC converter circuits 303a, 303b and 303c. 
If there is a motor for a peripheral axis of a robot such as a servo gun, besides the motors for driving the axes of the robot 320, the motor to be drivingly controlled is connected to one of the motor driving DC/AC converter circuits for the peripheral axes, e.g., the DC/AC converter circuit 303a. 
In the prior art example shown in FIG. 3, a motor driving controller that is formed of an AC/DC converter circuit and motor driving DC/AC converter circuits must be added for each motor for a peripheral axis of a robot to be controlled. Thus, the peripheral axes cannot be added at low cost. In the example shown in FIG. 4, moreover, the motor driving DC/AC converter circuits 211a, 211b and 211c as many as the motors for peripheral axes must be added, as well as the AC/DC converter circuit 210. In this case, the peripheral axes cannot be added at low cost either.
In the prior art example shown in FIG. 5, furthermore, the motor driving DC/AC converter circuits as many as the peripheral axes are previously located in the motor driving controller. If the controller is used in an application system that requires no peripheral axes, therefore, the added DC/AC converter circuits are useless, so that the controller is inevitably expensive. Since the motor driving DC/AC converter circuits are provided in advance, moreover, it is hard to select the motor type flexibly.